I tend to talk too much. Keep it short, and take action. Try to stick to one warning, then follow through with a consequence. With the water bottle, tell her to share, if she doesn't, just take it from her. In the tub, tell her not to put toys in the drain, then scoop her out of the tub if she tries it again. The less emotional you get the better- try to be calm and assertive, then ignore the protests. Very matter of fact.
Now, all of that is easier said than done. Even though I have 4 kids, and *know* what to do, I still tend to yell and do what I call "couch parenting"- where I talk too much and don't get up and deal with the issue fast enough.
5 yr olds can be uber-annoying. Hang in there.

__________________SaraWife to Bret , Mom to Kodi 9-10-00 , Owen 4-21-06 , Luke 8-21-07 , and our miracle baby, June 8-4-09 I'm ashamed of what I did for a Klondike Bar...